Active matrix liquid crystal image generator

Abstract

A system for producing spatially modulated monochrome or color light having gray scale includes an active matrix liquid crystal spatial light modulator having light modulating means including (i) a layer of ferroelectric liquid crystal material which is designed to switch between ON and OFF states and (ii) active matrix means including VLSI circuitry for dividing the layer of liquid crystal material into an array of individual liquid crystal pixels and for causing each of the pixels of liquid crystal material to modulate light individually by switching between the ON and OFF states in a way that depends upon the data which the VLSI circuitry is written. The system also includes illumination means having a light source for directing light from the source into the pixel-divided layer of ferroelectric liquid crystal material in a specific way. And finally, the system includes means for writing the VLSI circuitry with preselected data in accordance with a particular data ordering scheme such that the circuitry, in response to the written data, causes the pixels of liquid crystal material to individually switch between their ON and OFF states and therefore modulate light from the source in a way which, depending upon the data, produces a specific overall pattern of gray scale light.

What is claimed is: 
     
       1. A system for producing modulated light having gray scale, said system comprising: (a) an active matrix liquid crystal spatial light modulator having (i) light modulating means including a layer of ferroelectric liquid crystal material which is designed to switch between ON and OFF states, and   (ii) active matrix means including VLSI circuitry for dividing said layer of liquid crystal material into an array of individual liquid crystal pixels and for causing each of said pixels of liquid crystal material to modulate light individually by switching between said ON and OFF states in a way that depends upon the data which the VLSI circuitry is written, said VLSI circuitry of said active matrix means including an array of subcircuits, each subcircuit of which is dedicated to and defines a specific one of said pixels, said active matrix means dividing said layer of liquid crystal material into an array of immediately adjacent pixels, each of which has a maximum light modulating area of at most 100 square microns, said layer of ferroelectric liquid crystal material being maintained at a substantially uniform thickness of at most approximately 2 microns, whereby the size of said pixels can be made smaller than would be the case if the layer of liquid crystal were much thicker, for example of the order of 6 microns as required by nematic liquid crystal material in spatial light modulators;     (b) illumination means including a light source for directing light from said source into said pixel-divided layer of ferroelectric liquid crystal material in a specific way; and   (c) means for writing said VLSI circuitry with preselected data in accordance with a particular data ordering scheme such that said circuitry, in response to the data, causes said pixels of liquid crystal material to individually switch between their ON and OFF states and therefore modulate light from said source in a way which, depending upon said data, produces a specific overall pattern of gray scale light, said particular data ordering scheme being such that said data writing means writes each of said subcircuits, and therefore each of said pixels, with preselected data in a predetermined successive order, timewise, such that none of said subcircuits require auxiliary data storage buffer circuitry and therefore the complexity of said array of subcircuits can be reduced.   
     
     
       2. A system according to claim 1 wherein each of said pixels is square shaped, at most 10 microns on a side. 
     
     
       3. A system according to claim 1 wherein each of said subcircuits includes one and only one active component for modulating its associated pixel. 
     
     
       4. A system according to claim 3 wherein said active component of each subcircuit is a transistor. 
     
     
       5. A system according to claim 1 wherein said preselected data is digital data divided into individual digital data commands, one for each of said subcircuits and therefore each of said pixels, during any given time frame, each digital data command establishing the length of time its associated pixel is in its ON and OFF state during a given time frame. 
     
     
       6. A system according to claim 5 wherein each of said digital data commands establishes whether its associated pixel is in its ON or OFF state during each subframe of any given frame, whereby whether any given pixel is in its ON or OFF state during the various subframes of a given time frame determines the overall gray scale of that pixel during that time frame. 
     
     
       7. A system according to claim 6 wherein each of said digital commands comprises a series of binary bits, one bit for each of said subframes, each binary bit establishing whether its associated pixel is in its ON or OFF state during its associated subframe. 
     
     
       8. A system according to claim 5 wherein each of said given time frames is divided into a plurality of subframes for purposes of obtaining color, wherein each of said subframes is divided into a plurality of sub-subframes of predetermined time periods for purposes of obtaining colored gray scale, wherein said illumination means includes means for alternatively directing light of different colors, equal in number to the number of said subframes, into said pixel-divided layer of liquid crystal material during each successive subframe of each frame, and wherein each of said digital data commands establishes whether its associated pixel is in its ON or OFF state during each subframe and sub-subframe of any given frame, whereby whether any given pixel is in its ON or OFF state during the various subframes and sub-subframes of a given time frame determines the overall gray scale and color of that pixel during that time frame. 
     
     
       9. A system according to claim 8 wherein each of said digital commands comprises a series of binary bits, one for each of said sub-subframes, each binary bit establishing whether its associated pixel is in its ON or OFF state during its associated sub-subframe. 
     
     
       10. A system according to claim 9 wherein each of said subframes includes an additional blackout subframe after each of said first-mentioned subframes and wherein each of said digital data commands includes a binary bit associated with each of said blackout subframes for maintaining its associated pixel in an OFF state during its associated blackout subframe, each of said blackout subframes being sufficiently long to allow all of the pixels written during each immediately previous subframe to respond fully and to allow said illumination means to switch colors before the writing means begins writing the pixels in the next subframe. 
     
     
       11. A system according to claim 1 wherein the duration of the subframes, if arranged in order of duration, increase by a factor of two. 
     
     
       12. A system according to claim 1 wherein said illumination means including said light source includes means for directing light of different colors into said pixel-divided layer of ferroelectric liquid crystal material in a specific way so as to produce modulated colored light having gray scale and a polarizer/analyzer designed to pass light across a broad color band including light of said different colors. 
     
     
       13. A system according to claim 1 wherein said illumination means includes at least one light emitting diode serving as said light source. 
     
     
       14. A system according to claim 13 wherein said light emitting diode is the sole source of light of said illumination means. 
     
     
       15. A system according to claim 13 wherein said illumination means includes at least three light emitting diodes serving as said light source, each of which is a different color from the others. 
     
     
       16. A system according to claim 15 wherein said three light emitting diodes are red, green and blue light emitting diodes. 
     
     
       17. A system according to claim 1 including means for viewing the light modulated by said layer of liquid crystal material, whereby said system serves as a light display. 
     
     
       18. A system for producing modulated light having gray scale, said system comprising: (a) an active matrix liquid crystal spatial light modulator having (i) light modulating means including a layer of ferroelectric liquid crystal material which is designed to switch between ON and OFF states, and   (ii) active matrix means including VLSI circuitry for dividing said layer of liquid crystal material into an array of individual liquid crystal pixels and for causing each of said pixels of liquid crystal material to modulate light individually by switching between said ON and OFF states in a way that depends upon the data which the VLSI circuitry is written, said VLSI circuitry of said active matrix means including an array of subcircuits, each of which is dedicated to and defines a specific one of said pixels, said layer of ferroelectric liquid crystal material being maintained at a substantially uniform thickness of at most approximately 2 microns, whereby the size of said pixels can be made smaller than would be the case if the layer of liquid crystal were much thicker, for example of the order of 6 microns as required by nematic liquid crystal material in spatial light modulators;     (b) illumination means including a light source for directing light from said source into said pixel-divided layer of ferroelectric liquid crystal material; and   (c) means for writing said VLSI circuitry with preselected data in accordance with a particular data ordering scheme such that said circuitry, in response to the data, causes said pixels of liquid crystal material to individually switch between their ON and OFF states for a plurality of subframes which make up a given time frame and therefore modulate light from said source in a way which, depending upon said data, produces a specific overall pattern of gray scale light, said particular data ordering scheme being such that said data writing means writes each of said subcircuits and therefore each of said pixels with preselected data in a predetermined successive order, timewise, such that none of said subcircuits require auxiliary data storage buffer circuitry and therefore the complexity of said array of subcircuits can be reduced.   
     
     
       19. A system according to claim 18 wherein said active matrix means divides said layer of liquid crystal material into an array of immediately adjacent pixels, each of which has a maximum light modulating area of at most 100 square microns. 
     
     
       20. A system according to claim 19 wherein each of said pixels is square shaped, at most 10 microns on a side. 
     
     
       21. A system according to claim 18 wherein each of said subcircuits includes one and only one active component for modulating its associated pixel. 
     
     
       22. A system according to claim 21 wherein said active component of each subcircuit is a transistor. 
     
     
       23. A system according to claim 18 wherein said preselected data is digital data divided into individual digital data commands, one for each of said subcircuits and therefore each of said pixels, during any given time frame, each digital data command establishing the length of time its associated pixel is in its ON and OFF state during a given time frame. 
     
     
       24. A system according to claim 23 wherein each of said digital commands comprises a series of binary bits, one bit for each of said subframes, each binary bit establishing whether its associated pixel is in its ON or OFF state during its associated subframe. 
     
     
       25. A system according to claim 24 wherein: (a) said illumination means includes means for directing light of different intensities from said light source into said pixel-divided layer of ferroelectric liquid crystal material,   (b) each of said frames includes an additional blackout subframe between each of said first-mentioned subframes; and   (c) each of said digital data commands includes a binary bit associated with each of said blackout subframes for maintaining its associated pixel in an OFF state during its associated blackout subframe, each of said blackout subframes being sufficiently long to allow all of the pixels written during each immediately previous first-mentioned subframe to fully respond and to allow said illumination means to switch the intensity of said light source before the writing means begins writing the pixels in the next first-mentioned subframe.   
     
     
       26. A system according to claim 18 wherein said plurality of subframes is a plurality of subframes of equal time periods. 
     
     
       27. A system according to claim 18 wherein each of said given time frames is divided into a plurality of color subframes for purposes of obtaining color, wherein each of said color subframes is divided into a plurality of sub-subframes of predetermined time periods for purposes of obtaining colored gray scale, wherein said illumination means includes means for alternatively directing light of different colors, equal in number to the number of said subframes, into said pixel-divided layer of liquid crystal material during each successive subframe of each frame, and wherein each of said digital data commands establishes whether its associated pixel is in its ON or OFF state during each color subframe and sub-subframe of any given frame, whereby whether any given pixel is in its ON or OFF state during the various color subframes and sub-subframes of a given time frame determines the overall gray scale and color of that pixel during that time frame. 
     
     
       28. A system according to claim 27 wherein each of said digital commands comprises a series of binary bits, one for each of said sub-subframes, each binary bit establishing whether its associated pixel is in its ON or OFF state during its associated sub-subframe. 
     
     
       29. A system according to claim 28 wherein each of said color subframes includes an additional blackout subframe after each of said first-mentioned color subframes and wherein each of said digital data commands includes a binary bit associated with each of said blackout subframes for maintaining its associated pixel in an OFF state during its associated blackout subframe, each of said blackout subframes being sufficiently long to allow all of the pixels written during each immediately previous color subframe to respond fully and to allow said illumination means to switch colors before the writing means begins writing the pixels in the next color subframe. 
     
     
       30. A system according to claim 18 wherein said illumination means including said light source includes means for directing light of different colors into said pixel-divided layer of ferroelectric liquid crystal material in a specific way so as to produce modulated colored light having gray scale and a polarizer/analyzer designed to pass light across a broad color band including light of said different colors. 
     
     
       31. A system according to claim 18 wherein said illumination means includes at least one light emitting diode serving as said light source. 
     
     
       32. A system according to claim 31 wherein said light emitting diode is the sole source of light of said illumination means. 
     
     
       33. A system according to claim 31 wherein said illumination means includes at least three light emitting diodes serving as said light source, each of which is a different color from the others. 
     
     
       34. A system according to claim 33 wherein said three light emitting diodes are red, green and blue light emitting diodes. 
     
     
       35. A system according to claim 18 including means for viewing the light modulated by said layer of liquid crystal material, whereby said system serves as a light display. 
     
     
       36. A system for producing modulated light having gray scale during a given period of time comprising: (a) a spatial light modulator including a plurality of light modulating pixels switchable between different states so as to act on light in different ways during a plurality of light modulating subperiods making up said period of time said pixels being arranged in specific groups of said pixels;   (b) illumination means for directing light of either different brightnesses or different colors alternately and successively into said light modulating pixels during predetermined ones of said light modulating subperiods of said period; and   (c) switching means, responsive to preselected data signals, for switching said pixels to certain light modulating states in a controlled way during each light modulating subperiod of said period in order to modulate said light directed into said light modulating pixels during said light modulating subperiods, said switching means including means for simultaneously switching each of said groups of pixels, one group at a time, during each of said subperiods, said period further including a blackout subperiod during which said switching means switches all of said pixels to an OFF state in response to said preselected data signals in order to black out said light directed into said pixels thereby allowing either the brightness or the color of said light directed into said pixels by said illumination means to be changed without effecting the gray scale of said modulated light during said period.   
     
     
       37. A system according to claim 36 wherein said pixels are arranged in rows and columns and wherein said specific groups consist of the rows making up said rows and columns. 
     
     
       38. A system according to claim 36 wherein said light modulating subperiods making up said time period are unequal in duration. 
     
     
       39. A system according to claim 38 wherein said light modulating subperiods making up said time period, if arranged in order of duration, would double in duration from light modulating subperiod to light modulating subperiod. 
     
     
       40. A system according to claim 36 wherein said light modulating pixels include a ferroelectric liquid crystal light modulating material. 
     
     
       41. A system according to claim 36 wherein said switching means includes active matrix VLSI circuitry. 
     
     
       42. A method of producing modulated light having gray scale during a given period of time, the method comprising the steps of: (a) providing a spatial light modulator including a plurality of light modulating pixels switchable between different states so as to act on light in different ways during a plurality of light modulating subperiods making up said period of time, said pixels being arranged in specific groups of said pixels;   (b) directing light of either different brightnesses or different colors alternately and successively into said light modulating pixels during predetermined ones of said light modulating subperiods of said period;   (c) in response to preselected data signals, switching said pixels to certain light modulating states in a controlled way during each light modulating subperiod of said period in order to modulate said light directed into said light modulating pixels during said light modulating subperiods, each of said groups of pixels being switched into their light modulating states, one group at a time during each of said subperiods; and   (d) in response to said preselected data signals, switching all of said pixels to an OFF state during a blackout subperiod in order to black out said light directed into said pixels thereby allowing either the brightness or the color of said light directed into said pixels to be changed without effecting the gray scale of said modulated light during said period.   
     
     
       43. A method according to claim 42 wherein said pixels are arranged in rows and columns and wherein said specific groups consist of the rows making up said rows and columns. 
     
     
       44. A method according to claim 42 wherein said light modulating subperiods making up said time period are unequal in duration. 
     
     
       45. A method according to claim 44 wherein said light modulating subperiods making up said time period, if arranged in order of duration, would double in duration from light modulating subperiod to light modulating subperiod. 
     
     
       46. A method according to claim 42 wherein said light modulating pixels include a ferroelectric liquid crystal light modulating material. 
     
     
       47. A method according to claim 42 wherein said step of switching said pixels includes the step of switching said pixels using active matrix VLSI circuitry. 
     
     
       48. A method of displaying gray scale or color images, the method comprising the steps of: (a) providing an array of light modulating pixels organized in rows, each pixel being switchable between a first pixel state and a second blackout pixel state in response to input data;   (b) switching all of said pixels to said second blackout pixel state;   (c) after all of said pixels have been switched to said second blackout pixel state, illuminating said array of pixels with light of a first desired brightness and color;   (d) while said array of pixels is being illuminated with said desired brightness and color of light, switching the states of said pixels in each of said rows such that said array of pixels forms a desired pattern of modulated light, at least some of said rows of pixels being switched at different times from other ones of said rows;   (e) switching all of said pixels to said second blackout pixel state a second time in such a manner that the time interval between the time at which the states of the pixels in each row are switched to form said desired pattern of modulated light and the time at which that row is switched to said second blackout pixel state said second time is the same for each row of pixels; and   (f) after all of said pixels have been switched to said second blackout pixel state said second time, illuminating said array of pixels with light of a second desired brightness and color.   
     
     
       49. A method according to claim 48 wherein said steps of switching said pixels includes the step of switching said pixels one row at a time. 
     
     
       50. A method according to claim 48 wherein the step of switching the states of said pixels in each of said rows such that said array of pixels forms a desired pattern of modulated light includes the step of switching the states of said pixels in each of said rows a plurality of times such that said array of pixels forms a desired pattern of modulated light. 
     
     
       51. A method according to claim 50 wherein the pixels are switchable between only said first and second pixel states. 
     
     
       52. A method according to claim 48 wherein said array of pixels is an active matrix array of pixels including an array of subcircuits, each subcircuit of which is dedicated to and defines a specific one of said pixels, said array of subcircuits being configured such that none of said subcircuits require auxiliary data storage buffer circuitry for storing said input data in order to use said input data to switch the states of said pixels and therefore the complexity of said array of subcircuits can be reduced. 
     
     
       53. A method according to claim 52 wherein the steps of illuminating said array of pixels includes the step of illuminating the array of pixels with polarized light of a particular polarization and wherein said array of pixels is an array of light modulating pixels that modulate the polarization of the light between a first polarization state when said pixels are switched to said first pixel state and a second polarization state when said pixels are switched to said second pixel state. 
     
     
       54. A method according to claim 48 wherein said array of pixels is an array of pixels including a layer of ferroelectric liquid crystal material that acts as a light modulating medium switchable between said first and second states. 
     
     
       55. A method according to claim 48 wherein said second blackout pixel state is a pixel state which prevents any of the light illuminating any pixel switched to the blackout pixel state from contributing to the image. 
     
     
       56. A method according to claim 48 wherein said steps of illuminating said array of pixels includes the step of using at least one individually controllable light emitter which emits light of a predetermined color to illuminate said array of pixels. 
     
     
       57. A method according to claim 48 wherein said steps of illuminating said array of pixels includes the step of using a broad spectrum light source and a color wheel to illuminate said array of pixels.